Track count method for an optical disc in an optical disc system
A method for counting a number of tracks of an optical disc in an optical disc system. The optical disc system includes an optical pickup, a light source, and a plurality of optical sensors. The method includes emitting a light beam to the optical disc from the light source, detecting light reflected from the optical disc by the optical sensors, and generating a tracking error signal according to detected signals of the optical sensors while the optical pickup moves along a radial direction of the optical disc. The method further includes generating a tracking error zero crossing signal according to the tracking error signal, generating a peak detecting signal according to the tracking error signal, generating a pseudo radio frequency zero crossing signal according to the peak detecting signal, and generating a track count signal according to the pseudo frequency crossing signal.
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1. Field of the Invention
The present invention relates to a track count method for an optical disc in an optical disc system, and more particularly, to a track count method which generates track count signals based on generating a pseudo radio frequency zero crossing signal.
2. Description of the Prior Art
Before an optical pickup starts to read/record data from/to a compact disc or a digital versatile disc (DVD), it has to move to a target track of the compact disc or the DVD. When the optical pickup searches for the target track it crosses other tracks. The distance between the present location of the optical pickup and the target track can roughly be divided into two possible situations, short-term track crossing(short seek) and long-term track crossing(long seek). In both of these situations, the relative speed and direction between the optical pickup and the optical disc are important factors when an optical disc system controls the optical pickup to cross tracks. Only when the optical system has confirmed the moving direction of the optical pickup, can it accurately control asled motor to move the optical pickup to the target track so to read/record data from/to the optical disc. While the optical disc system controls the optical pickup to cross tracks, it constantly confirms the moving direction of the optical pickup.
Typical methods of confirming the moving direction of the optical pickup vary according to the speed of the optical pickup when it crosses tracks. When the moving speed of the optical pickup is slow, the optical disc system uses the optical pickup to emit light to a groove or a land of the optical disc for generating a reflected radio frequency ripple signal and a tracking error signal, which depends whether the light is reflected from the target track or not. A phase difference between the radio frequency ripple signal and the tracking error signal is used to determine the moving direction of the optical pickup. A DVD-RAM disc stores data on both grooves and lands to increase a capacity for data. Therefore, as shown in
It is therefore a primary objective of the claimed invention to provide a track count method for an optical disc in an optical disc system to solve the above-mentioned problem.
According to the claimed invention, the optical disc system comprises an optical pickup that is moveable along a radial direction of the optical disc, a light source installed on the optical pickup for emitting light, and a plurality of sensors installed on the optical pickup for detecting light reflected from the optical disc. The method comprises using the light source to emit light towards the optical disc, using the sensors to detect light reflected from the optical disc, and generating a tracking error (TE) signal based on the light received by the sensors while the optical pickup moves along a radial direction of the optical disc. The method further comprises generating a tracking error zero crossing (TEZC) signal based on the TE signal, generating a peak detecting (PD) signal based on the TE signal, generating a pseudo radio frequency zero crossing (RFZC) signal based on the PD signal, and generating a track count signal based on the TEZC signal and the pseudo RFZC signal.
It is an advantage of the claimed invention that the track count method for an optical disc in an optical disc system can generate the pseudo RFZC signal with better quality than the radio frequency ripple signal used in the prior art so that the optical disc system reads/records data from/to the optical disc more accurately by using the signal with better quality.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that illustrated in the various figures and drawings.
BRIEF DESCRIPTION OF DRAWINGSThe method of arranging data units upon a digital versatile disc-random access memory (DVD-RAM) is different from that of a digital versatile disc (DVD). To increase the capacity for data, the DVD-RAM stores data on both grooves and lands. Based on this difference, the method of controlling an optical pickup for the DVD-RAM is also different from that of the DVD. For the DVD-RAM, a tracking error signal is generated by a differential push pull (DPP), and the optical pickup has to cross a groove and a land for generating a circle of tracking error signals so that it can be more easily controlled during searching. However, the frequency of the radio frequency ripple signal generated by the data area is twice that generated by the blank area because the DVD-RAM stores data on both grooves and lands. As shown in
Please refer to FIG. 2.
As shown in
Please refer to FIG. 5.
In contrast to the prior art, the present invention generates a pseudo radio frequency zero crossing signal with a better quality than the radio frequency ripple signal used in the prior art, so that it can improve the performance of the optical disc system 20 by using the signal with better quality.
Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teaching of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
Claims
1. A track count method for an optical disc in an optical disc system, the optical disc system comprising an optical pickup moveable along a radial direction of the optical disc, a light source installed on the optical pickup for emitting light, and a plurality of sensors installed on the optical pickup for detecting light reflected from the optical disc, the method comprising:
- using the light source to emit light towards the optical disc;
- using the sensors to detect light reflected from the optical disc;
- generating a tracking error (TE) signal based on the light received by the sensors while the optical pickup moves along a radial direction of the optical disc;
- generating a tracking error zero crossing (TEZC) signal based on the TE signal;
- generating a peak detecting (PD) signal based on the TE signal;
- generating a pseudo radio frequency zero crossing (RFZC) signal based on the PD signal; and
- generating a track count signal based on the TEZC signal and the pseudo RFZC signal.
2. The method of claim 1 wherein the TEZC signal is inverted whenever the TE signal is zero.
3. The method of claim 1 wherein the optical disc system further comprises an A/D (analog to digital) converter for converting the TE signal into a series of digital signals, a first comparator connected to the A/D converter which allows digital signals greater than a first threshold to pass through, a second comparator connected to the A/D converter which allows digital signals lower than a second threshold to pass through, a detector connected to the first and second comparators for detecting local maximums and local minimums of the TE signal according to the digital signals which pass through the first or second comparator, and a signal generator connected to the detector for generating the PD signal according to the local maximums and local minimums of the TE signal; the method further comprising:
- using the A/D converter to convert the TE signal into the digital signals;
- using the first comparator to compare the digital signals with the first threshold so as to allow digital signals greater than the first threshold to pass through;
- using the second comparator to compare the digital signals with the second threshold so as to allow digital signals lower than the second threshold to pass through;
- using the detector to detect local maximums and local minimums of the TE signal according to the digital signals which pass through the first or second comparator; and
- using the signal generator to generate the PD signal according to the local maximums and local minimums of the TE signal.
4. The method of claim 3 further comprising:
- using the digital signals which pass through the first or second comparator to calculate a plurality of local average values each being an average of a plurality of consecutive digital signals which pass through the first or second comparator; and
- comparing the local average values to determine the local maximums and local minimums of the TE signal.
5. The method of claim 3 wherein when the optical pickup moves towards a center of the optical disc, the pseudo RFZC signal is in phase with the PD signal;
- the optical disc system further comprises an inverter connected to the signal generator; and when the optical pickup moves away from the center of the optical disc, the PD signal is inverted by the inverter to generate the pseudo RFZC signal.
6. The method of claim 3 wherein the PD signal is inverted whenever the TE signal reaches a local maximum or a local minimum.
7. The method of claim 3 further comprising:
- setting an initial level of the PD signal according to a radial inward or outward moving direction of the optical pickup.
8. The method of claim 1 wherein data is stored on grooves and lands of the optical disc.
9. The method of claim 8 wherein the optical disc is a DVD (digital versatile disc).
10. The method of claim 9 wherein the optical disc is a DVD-RAM (digital versatile disc random access memory).
11. A method for generating a pseudo radio frequency zero crossing (RFZC) signal in an optical disc system, the optical disc system comprising an optical pickup moveable along a radial direction of an optical disc, the optical pickup emitting light to the optical disk and detecting light reflected from the optical disc so as to generating a radio frequency (RF) signal, the method comprising:
- generating a tracking error (TE) signal according to the RF signal;
- generating a peak detecting (PD) signal according to the TE signal; and
- generating the pseudo RFZC signal according to the PD signal.
12. The method of claim 11 further comprising generating a track count signal according to the pseudo RFZC signal.
13. The method of claim 11 further comprising generating a tracking error zero crossing (TEZC) signal according to the TE signal, wherein the TEZC signal is inverted whenever the TE signal is zero.
14. The method of claim 13 further comprising generating a track count signal according to the TEZC signal and the pseudo RFZC signal.
15. The method of claim 11 wherein the optical disc system further comprises an A/D (analog to digital) converter for converting the TE signal into a series of digital signals, a first comparator connected to the A/D converter which allows digital signals greater than a first threshold to pass through, a second comparator connected to the A/D converter which allows digital signals lower than a second threshold to pass through, a detector connected to the first and second comparators for detecting local maximums and local minimums of the TE signal according to the digital signals which pass through the first or second comparator, and a signal generator connected to the detector for generating the PD signal according to the local maximums and local minimums of the TE signal; the method further comprises:
- using the A/D converter to convert the TE signal into the digital signals;
- using the first comparator to compare the digital signals with the first threshold so as to allow digital signals greater than the first threshold to pass through;
- using the second comparator to compare the digital signals with the second threshold so as to allow digital signals lower than the second threshold to pass through;
- using the detector to detect local maximums and local minimums of the TE signal according to the digital signals which pass through the first or second comparator; and
- using the signal generator to generate the PD signal according to the local maximums and local minimums of the TE signal.
16. The method of claim 15 further comprising:
- using the digital signals which pass through the first or second comparator to calculate a plurality of local average values each being an average of a plurality of consecutive digital signals which pass through the first or second comparator; and
- comparing the local average values to determine the local maximums and local minimums of the TE signal.
17. The method of claim 15 wherein when the optical pickup moves towards a center of the optical disc, the pseudo RFZC signal is in phase with the PD signal; the optical disc system further comprises an inverter connected to the signal generator; and when the optical pickup moves away from the center of the optical disc, the PD signal is inverted by the inverter to generate the pseudo RFZC signal.
18. The method of claim 15 wherein the PD signal is inverted whenever the TE signal reaches a local maximum or a local minimum.
19. The method of claim 15 further comprising:
- setting an initial level of the PD signal according to a radial inward or outward moving direction of the optical pickup.
20. The method of claim 11 wherein the optical disc is a DVD-RAM (digital versatile disc-random access memory).
Type: Grant
Filed: Feb 20, 2007
Date of Patent: Mar 30, 2010
Assignee: Mediatek Inc. (Hsin-Chu)
Inventors: Shung-Yunn Wang (Hsin-Chu Hsien), Hao-Cheng Chen (Taipei Hsien)
Primary Examiner: Paul Huber
Attorney: Winston Hsu
Application Number: 11/708,146
International Classification: G11B 7/00 (20060101);